Tuesday, June 1, 2010

BASICS FOR THE CHEMICAL TANKERMAN -- CAPT AJIT VADAKAYIL

FOR CHEMICAL TANKER DECK OFFICERS AND SAILORS --

A parcel chemical man must know the basics. Or he cannot run a SAFE and efficient chemical parcel tanker.

On Chemical tankers we have lot of " Shakespeares " who do NOT know English alphabets A B C D -- etc-- it is so pathetic . The Superintendents and Supercargoes who direct you from ashore are even worse pretenders --

BE SAFE -- Ignorance is NOT bliss, in this dangerous field.

SLOG LESS - Most of the time spent in tank cleaning is fruitless--

READ ON--

Everything you see on this planet is made out of 118 atomsor elements. Atomic number 118 belongs to Ununoctium.

Take a pure silver coin and keep splitting it into two halves and discard one of them . Keep repeating and soon enough you will not be able to see it visually but only under a sensitive microscope. Continue dividing and finally you have a piece of silver which cannot be divided any more . This piece is the atom or element we are referring to.

Whatever you see around you unless it is an extra-terrestrial object like a Shiva lingum ( this is a black stone found in Indian temples ) is made out of a combination of these atoms.

Everything made by combining these atoms tend to go back to its mother state as a natural tendency, on passage of time . That however does not give you license to flout Marpol regulations or throw plastics overboard.

All elements heavier than lead are unstable and radioactive

An inorganic chemical does not have a carbon atom. It is made of a combination of the remaining 118 atoms or elements. These atoms are joined together by electrovalent bonds giving rise to simple and small number of compounds. Inorganic reactions are ionic and fast.

An organic chemical must contain the carbon atom as a rule. Carbon is combined with atoms of hydrogen, oxygen, nitrogen, sulphur, phosphorous etc . The carbon atoms are joined together by covalent bonds to form long chains or rings thus giving rise to a large number of complex compounds we carry on parcel chemical tankers. Reactions are non ionic and slow. Hydrocarbon gases have upto 4 carbon atoms. Liquids have 5 to 19 and gases have more than 20 carbon atoms.

In the middle of the atom is the nucleus. The nucleus contains protons(+) and neutrons. Revolving around the nucleus in elliptical orbits are electrons.(-). The only reason all 118 atoms are different from each other is because the count of protons , neutrons and electrons are different. The number of electrons and protons of an atom are equal. For example the carbon atom has 6 electrons and 6 protons. The number may be equal but the proton mass is 1832 times that of an electron. Copper has 29 of each. Silver has 47 of each.. The atomic number of an element is the number of protons in the nucleus. Carbon’s atomic number is 6.

An acid is a proton donor, a base is a proton acceptor.

Acids are neutralized by reaction with bases and vice versa.

Organic acids are flammable. They react with metals to give off Hydrogen.

Organic bases are flammable, and many are reducing agents. A base which is soluble in water is called an Alkali.

The model of the atom is similar to our solar system ( only for understanding purposes). Nucleus is the sun, electrons are planets. The atom is thus mostly empty space as the planets are far from the sun. Electrons can exist as part of an atom or in the free state. The science of electronics was possible by the ability of a heated metal cathode to emit a continious stream of electrons into a electron tube.

A molecule is a particle made out of 2 or more atoms. An electrical bond hold atoms together in a molecule. Benzene is a flat molecule with Carbon/ Hydrogen lying in the same plane at 120 degrees. Hydrocarbon molecules have Carbon and Hydrogen atoms in various arrangements.

Many chemicals are reactive with themselves. Such reaction may result in the formation of larger molecules. Polymerisation, (like crazy glue) or the disintegration of molecules ( decomposition). Polymerisation happens molecules which link together into a larger unit containing anything from 2 to thousands of molecules .

Capillarityis the attraction between the molecules which results in the rise of a liquid in small tubes.

Brownian movement is the continious zig zag movemenbt of particles in a colloidal suspension, caused by impact of molecules of liquid on the colloidal particles.

The plasmacutter we use for cutting stainless steel can develop temperatures upto 28000 deg C. Plasma results when a gas is heated to heated to a high temperature and changes into positive ions, neutral atoms and negative electrons and is generally considered the fourth state of matter—the other 3 being solids, liquids and gases.

Protons have positive charge, electrons have negative charge of equal strength and neutrons have no charge at all. Since the number of electrons and protons are the same the atom has no resultant charge and is neutral.

The protons and neutrons are held together very tightly in the nuclues. But the outer orbital electrons are held very loosely. They can jump from one atom to another. It is also possible to shift electrons from one atom to another. The atom which loses one electron has one excess proton as a result in the tight nucleus and thus gets unbalanced. Such an atom is called a positive ion.

The atom which receives an excess electron is also unbalanced and is called a negative ion. Positive and negative ions are thus all the time trying to give up or receive an electron which they need. There is a mutual attraction between them like between a boy and a girl searching for a soulmate. When a postive and negative ion are kept apart there is static electricity. When they are brought close without touching the excess electrons from a negative ion jumps across till both become neutral accompanied by light and sound --like lightning and thunder.

When you rub a plastic scale on your hand the skin loses electrons. Air, skin, glass, hair, nylon wool etc lose electrons. On the contrary polyster rubber, pvc , teflon etc easily absorb electrons. The more the rubbing, the larger the charge. It is not the friction which does this. Rather it is the increase in contact area. Again, an atom which has gained or lost electrons is said to be ionised. Now you have a general idea what is DI ( de ionised )water which you so gleefully spray on your tank bulkheads.

An ion often has entirely different properties from the atom from which it was formed. Ion formation increases the bp and reduces the freezing point.

Some materials hold their electrons very tightly. Electrons are not allowed to wander . These materials are called insulators. Examples are glass , plastic, dry air etc.

Some materials on the contrary have electrons held very loosely which wander through very easily. These materals are called conductors. Examples are metals. Free electrons wander through a metal conductor aimlessly, but remember the conductor as a whole remains electrically neutral. A good conductor has lot of free electrons in the outer orbit.

The flow of electrons in a conductor is random and not to any certain direction. 6.28 x 10 raised to 18 electrons per second is thus called one ampere. If you visualise a water tank with a drain cock and tube at the bottom—the level of water in tank is potential difference in volts (E) , the thickness of tube is resistance in ohms(R), and the quantity of water flow through the tube is current amperes(I).

The basic electrical formula we all know is--

I =E / R.

So then what kills amperes or volts? Think about it !!

0.100– 0.200 Amperes (death) this range generally causes Fibrillation of the heart. when the heart is in this condition, it vibrates at a fast rate like a “quiver” and

ceases to pump blood to the rest of the body.

0.060– 0.100 A (extreme difficulty in breathing)

0.030– 0.040 A (muscular paralysis)

0.020– 0.030 A (unable to let go of the circuit)

0.010– 0.020 A (very painful)

Like charges repel and unlike charges attract. But a charged object can also attract something which is neutral.

When you walkdown a ships alleyway stairway in absolute darkness on a cold dry day and slide yor hand on the plastic sheath of the handrail you can actually see electrons jumping from your finger tips to the metal frame accompanied by tiny shocks. When the air is humid the water in the air removes free electrons from your body and thus it cannot build up a charge which can give a nasty shock. So then what is a spark. It is a sudden rush of electrons. Having said this what is electricity? It is a flow of free electrons of the metal wire.

AC supply of 50 Hertz or Cycles per second becomes negative 50 times , positive 50 times and zero 100 times every second. The filament of an electric bulb lights up because it does not get the time to cool down. An incendive spark is what can cause an explosion. This is the reason why on chemical tankers who carry static accumulator chemicals the bottom one foot of all all railings on deck, the paint is stripped off to bare metal.

Shake up a metal can containing Toluene or Kerosene and bring it very close to a metal surface in a dark room. You can see the jumping electrons for yourself --like arc welding.

The reason why the human body conducts electricity is due to salt in your blood and cells.

A positive ion is called a cationand negative ion is called anion.

A non bonded projecting object can become a potential electrode of spark promoter collecting the charge from the liquid.when it is close enough to an earth the spark promoter instantaneously releases its charge in an arc ( spark ). When a charged liquid flows into the ships tank it attracts a charge of same size but of opposite polarity to the inner bulkheads of tank.

Charge relaxation depends on the conductivity of the liquid.. There can be high voltage at the surface of the liquid called surface voltage. At high surface voltage with sufficient potential difference a spark can jump to the liquid surface. Such a phenomenon is called brush incendive discharge and can cause an explosion., which causes ignorant souls to scratch their collective heads.

On chemical tankers you will find that protruding objects like high level alarm and fixed tank cleaning machines inside the cargo tank are properly earthed. A Toluene deck tank is also securely earthed—your ship can fail a risk assessment inspection if not.

Even to run a proper engine room you need to know about static electricity charges. With modern engines being fitted with nominal 10 micron heavy oil fine filters ,without homogenisers–to keep colloids apart which have been coagulated by the centrifuging action of purifier. .

Modern sewage treatment plants use cataphoresis. Sewage water contains colloids which carry electric charge and do not settle down easily. Thses particles can be removed by cataphoresis in which sewage water is passed through a tunnel fitted with metallic electrodes maintained at high potential difference.the charged particles migrate to oppositely charged electrodes and get neutralisedand gets coagulated and settle down.. The deposited water is used as manure and clean water for irrigation or even drinking.

An ionic bond results from the transfer of electron ( structural unit is ions ) while a covalent bond results from the sharing of electrons ( structural unit is molecules ).

A salt NaCl crystal is extremely strong and rigid. A sodium Na ion is equally attracted to 6 chloride Cl ions. These powerful interionic forces are overcome only at its melting point of 801 degree centigrade. NaCl is an ionic compound which has equal number of sodium cations and chloride anions.

Water is a good solvent for salt . It has a high di-electric constant or relative permitivity. ( 81 --it has no units ). This means the force of attraction between ions is 81 times less in water than in a vacuum and this allows them to separate. High di-electric constant is equivalent to high insulating properties to lower the attraction between the oppositely charged ions once they are solvated. Water solvates both cations and anions. When you do a chloride wall wash test rememer that a pinch of salt put in methanol remains there , and water is the best solvent.

When a solid or liquid dissolves the structural unit ions or molecules become separated from each other and the spaces in between become occupied by solvent molecules.

As per the Bronsted –Lowry theory ---an acid contains Hydrogen which when dissolved in water become disassociated and generates Hydrogen ions. An acid is termed as a substance that gives up a proton. The ease with which an acid loses a proton is known as its strength . Sulphuric acid and Hydrochloric acids are strong acids since they tend to give up a proton very readily. A proton is an acid because it is deficient in electrons and need an electron pair to complete its valence shell. Acids give hydrogen ions in aqueous solution. Acids react with metals and give off hydrogen. Acids have sour taste.

Some substances have more than one proton that can be given to a base. Such acids are known as polyprotic acids. Sulphuric acid is an example of a polyprotic acid, since it can lose two protons to the base water ( in other words it is a diprotic acid in two ionisation stages ).

As per the Bronsted –Lowry theory --a base is a substance that accepts a proton. The ease with which a base takes up a proton is called strength of a base. Base gives hydroxide ions in an aqueous solution. Bases have bitter taste and are slippery to touch.

It is there fore commonsense that an acid will react with a base by the transfer of a proton from the acid to the base.

When an acid and a base react to from salt and water, the process is known as neutralisation.

Some substances can act both as acids ( by losing an H+ion ) and as bases ( by gaining an H+ ion ). Such substances are known as amphiprotic substances or ampholytes. Water is such an example.

Bufferis a solution containing both a weak acid and its conjugate weak base. The weak acid becomes a buffer when alkali is added and vice versa.

Solutemolecules and ions do not exist in solution as naked particles.—they are solvated. Clinging to each dissolved particle is a cluster of solvent molecules held there by bonds. It was formation of these bonds that provided the energy to break the bonds that held solute particles together. The very fact that dissolution has taken place show that new bonds have taken the place of old ones.

According to the laws of electrostatics the stability of a charged system is increased by dispersal of charge.. Dispersal of charge by solvation tends to stabilise cations and anions . Water is the most common solvent as it can act as both an acid and a base. Solvents which have a greater tendency to accept a proton is called protophillic eg water, alchohol. Solvents which have a greater tendency to donate a proton is called protogenic eg water, acetic acid.

Most of the organic substances ( non polar ) dissolve in one another but not in water ( polar ). Similarly inorganic substances (polar ) are generally soluble in water and other polar solvents.

Most solids become more soluble with increase of temperature. The solvent must do more than simply being a broker to bring different molecules together so that they can react with each other. The solvent is involved in the reaction which takes place.

NaCl electrolyte is completely disassociated in solution. The tendency of ions to migrate and thus conduct electricity is retarded by the electrostatic attraction between cations and anions and also between ions and the solvent. As the concentration of this solution is increased the retarding effect is increased. So a fixed amount of NaCl is a better conductor when dissolved in a large amount of water because ions are further apart and exert less attraction upon one another and upon the solvent molecules.

Chemical behavior is determined by molecular structure. Crosslinking in rubber is brought about by vulcanising—heating with sulphur—which cause formation of sulphur bridges between molecules.

Two molecules with the same molecular formula but different constitutional formulas are called isomers.

Oxidationcan be termed as removal of hydrogen atom or addition of oxygen atom

Reductioncan be termed as addition of hydrogen atom or removal of oxygen atom

An atom/ ion/ molecule that donates electrons is called reducing agent while those which accepts electrons is called an oxidising agent.

Thus in corrosion a metal is oxidised by loss of electrons to oxygen and formation of oxides.

A substance that ionises in water to produce ions other than h+ and oh- is called a salt. Salt is produced by neutralisation.

Diffusion, is the flow of matter from a higher concentration to a lower concentration, resulting in an even distribution. the rate of diffusion is proportional to the cross-sectional area and to the gradient of concentration, temperature, or charge (when the gradient is small). diffusion is a molecular process, depending solely on the random motions of individual molecules. The rate of diffusion of matter is therefore directly proportional to the average velocity of the molecules—the diffusion coefficients of chemicals are known.

No lather can be produced unless all Calcium and Magnesium ions ( cations ) have been precipitated. Temporary hardness is removed by boiling for 15 min. The bicarbonates of Calcium and Magnesium will decompose to insoluble carbonates which settle as precipitate.

Permanent hardness is removed by adding washing soda. Na2Co3 10 H2O. So hardness is defined as concentration of Cal/ Mag cations in terms of Calcium Carbonate. Concentration is measured in degrees hardness. There are many units like American/ English/ French/ German hardness etc.

Hardness units: 1 ppm = 1 mg/l = 0.1 Fr = 0.07 Cl = 0.02 Meq/l

Fr = French Cl = Clarke Meq = milli equivalent

Good fresh water has a hardness of 2 while seawater has a hardness of 6800 mg/l

Seawater contains a lot of calcium/ magnesium and therefore has high water hardness. Some products like fatty acids and vegetable oils with a high free fatty acid content will formate white sticky residues ( calcium and magnesium soaps ) if they were cleaned with a water of a high water hardness ( eg. Sea water)

Soap is dispersed in spherical clusters called miscelleseach of which may contain hundreds of soap molecules. A soap molecule has a polar end which is water soluble (hydrophilic) and a and a non polar end which is not water soluble (hydrophobic ).

The non polar HC chains dissolve in each other. The polar groups dissolve in water. Similarly charged miscelles repel each other and prevent oil droplets from coalescing. A stable emulsionof oil and water forms and can be removed easily from the surface being cleaned. Hardwater contains Cal/ Mag salts which react with soap to form insoluble Cal/ Mag Carboxylates ( ring in the bath tub which always got your non-chemical chambermaid disgusted with your personal hygiene ).

C12 –C18 alcohols are used in enormous quantities to make detergents. Tensidein a detergent wraps up a particle and prevents it from redepositing. One end of the tenside molecule has affinity to water and the other is repellent to water. Emulsifier has a water seeking end and a oil seeking end. Emulsification does not involve chemical change. It just suspends particles of one product with another which gives rise to a milky appearance of solution.

Synthetic detergent molecules have a non polar end which is oil soluble and a polar end which is water soluble. The most widely used detergents are sodium salts of Alkyl Benzene Sulphonic acids.

Soft biodegradable detergents are Alkyl Suphates, Ethoxylates and their Sulphates and Alky Benzene Sulphonates. Sulphates and Sulphonates retain their efficiency in hard water since their correpsonding Cal/ Mag salts are soluble. Being salts of strong acids they yield neutral solutions in contrast with soaps which being salts of weak acids yield slightly alkaline solutions.

To dissolve an ionic compound the solvent must be highly polar. In addition it must have a high dielectric constant. Ie-- it must be a good insulator to lower the attraction between oppositely charged ions once they are solvated.

There are other liquids which have very large dipole moments and high dielectric constants and yet are very poor solvents for ionic compounds. What is needed is solvating power---the ability to form strong bonds to dissolved ions. Water owes a large part of its special solvating power to its OH- group. It solvates cations strongly through the unshared pairs on oxygen. It solvates anions strongly through hydrogen bonding.

Methanol resembles water in having an OH- group. It is not surprising that it too dissolves ionic compounds, However it is inferior to water as it is less polar. This is the reason why water must be added into the methanol wash before adding Silver Nitrate for the Chloride test.

Solvents such as water and methanol are called proticsolvents.----solvents containing Hydrogen that is attached to oxygen or nitrogen and hence is acidic enough to form Hydrogen bonds. Other protic solvents solvate ions in the same way that water does. –cations through unshared pairs and anions through hydrogen bonding.

Recent years have seen the development and wide spread use of polar aproticsolvents---solvents with moderately high dielectric constants which do not contain acidic hydrogen eg DMSO/ DMF/ HMPT. They dissolve ionic compounds but in a different way from protic solvents.. They cannot form hydrogen bonds to anions. Aprotic solvents dissolve ionic compounds chiefly through their solvation of cations. Water dissolves ionic compounds very well but is a poor solvent for most organic compounds. Non polar solvents like ether are good solvents for organic compounds but very poor solvents for inorganic salts. Methanol can be used for this. Aprotic solvents through their lipophilic (oil loving )portions dissolve organic compounds.they also dissolve inorganic compounds through solvation of cations. Aprotic solvents work at room temp efficiently.

DMSO:-

A change to an aprotic solvent can increase the tankcleaning reaction rate as much to a million fold. Among protic solvents, ionising power is highest for solvents that form the strongest hydrogen bonds ie the solvents with the most acidic Hydrogens. Aprotic solvents dissolve ionic reagents chiefly through their bonding to the cation. This leaves the anion free and highly reactive.

WATER SOLUBLITY

Soluble organic chemicals

Insoluble organic chemicals

Organic salts

Saturated hydrocarbons

Alcohols

Unsaturated hydrocarbons

Esters

Aromatic hydrocarbons

Ethers

Alkyl halides

Acids

Aryl halides

Amines

Nitriles

Amides

Ketones

Aldehydes

Position of functional group, branching, and the compactness of the molecule will affect solubility

Functional group toward center of molecule means increased water solubility

No comments:

Post a Comment

Followers

About Me

been in command of chemical tankers (mainly) for more than 6640 days -- spread over 30 years ( a world record! ) . My Chemical posts are free for ALL sailors on this planet . Any profit making person or institution publishing extracts, must clearly write " reproduced from ajitvadakayil.blogspot.com " ,- it pays to remember, that the chemical contents are patented . This blogsite will transform your mind . You yourself, are the teacher, the pupil, the messiah, the seeker, the traveller and the destination . It is no measure of health to be well adjusted to this profoundly sick society . I am from INDIA, the mother of all civilizations . I will be re-writing world history , and this will surely not gratify the evil hijackers of human history . Awaken your inner voice . Experience the joy of your own being . Your own conscience is the best interpreter . In a time of universal deceit, telling the truth is a revolutionary act . The naked truth can never be hate speech or defamation. This blogsite does not sacrifice truth on the altar of political correctness . You shall know the truth and the truth shall set you free . Dont ever underestimate the value of this blogsite .